Manufacturing of integrated circuits includes deposition of various materials onto patterned substrates, such as silicon wafers. These materials include metal and metal-containing layers, such as diffusion barriers/liners to prevent diffusion of copper (Cu) from copper-containing conducting layers into dielectric materials and seed layers that promote adhesion and growth of the Cu layers onto the substrate. As the minimum feature sizes of patterned substrates continues to shrink, deposition processes are required that can provide advanced layers on high-aspect ratio structures at sufficiently low temperatures.
Chemical vapor deposition (CVD) has seen increasing use for preparation of coatings and thin layers in semiconductor wafer processing. CVD is a favored deposition method in many respects; for example, because of its ability to provide highly conformal and high quality layers at relatively fast processing times. Further, CVD is beneficial in depositing layers on substrates of irregular shapes, including the provision of highly conformal layers despite the presence of deep contacts and other high aspect-ratio features. In general, CVD techniques involve the delivery of gaseous precursors (reactants) to the surface of a substrate where chemical reactions take place under temperature and pressure conditions that are favorable to the thermodynamics of the desired reaction. The type and composition of layers that can be formed using CVD may be affected by the ability to deliver the reactants or reactant precursors to the surface of the substrate.
In order for the device manufacturing process to be practical, the deposition processes must be carried out in a reasonable amount of time. This requirement can necessitate efficient delivery of a precursor containing a metal element or a non-metal element to a process chamber containing the substrate(s) to be processed. A common problem encountered in the deposition of materials by CVD techniques is a low deposition rate onto a substrate because the vapor pressure of the solid precursor is low and because of the transport issues associated with such low vapor pressures, thereby making the deposition process impractical. The low vapor pressure can limit the flow of the precursor through gas lines to the process chamber of the deposition system. In addition, many solid precursors can partially or completely dissociate prematurely in the precursor vaporization system upon heating, thereby limiting the temperature to which the precursors can be heated and the precursor vapor pressures.
For these and other reasons, it is desirable to provide apparatus and methods for efficiently delivering a precursor to a process chamber that overcome the various problems associated with conventional CVD deposition systems.